1. Field of the Invention
The present invention relates to a communication device, a communication control method, and a program, and particularly relates to a communication device, a communication control method, and a program that can improve user-friendliness of devices connected to multiple output terminals.
2. Description of the Related Art
In recent years, the HDMI® has become widespread as a communication interface for high-speed transmission of a baseband (uncompressed) image (video) signal and an audio signal associated with an image thereof.
The HDMI® specification is an interface specification for digital consumer electronics (home appliances). The specification is arranged for audio-visual (AV) electronics based on the Digital Visual Interface (DVI), which is a standard specification for connecting a personal computer (PC) and a display device.
There are three types of devices (referred to below as HDMI® devices) which are to be connected via HDMI®, namely, an HDMI® source, an HDMI® sink, and an HDMI® repeater.
The HDMI® source includes an output terminal from which an image or audio signal is output via HDMI®, and the HDMI® sink includes an input terminal to which the image or audio signal is input via HDMI®. The HDMI® repeater includes one or more input terminals and one or more output terminals to act as both the HDMI® source and the HDMI® sink.
The HDMI® includes a transition minimized differential signaling (TMDS) channel, a consumer electronics control (CEC) line, and other channels. The TMDS channel is a signaling channel through which a baseband image or audio signal is transmitted in one direction from the HDMI® source to the HDMI® sink via the appropriate HDMI® repeater. The CEC line is a bidirectional control channel used in controlling the HDMI® source, the appropriate HDMI® repeater, and the HDMI® sink.
That is, the HDMI® uses the TMDS channel for the physical layer and uses the CEC line for connection of an overall control system for devices connected with HDMI®.
Also, the HDMI® uses the High-bandwidth Digital Content Protection (HDCP) to encrypt a signal for fulfilling a copyright protection function.
Further, the HDMI® uses the Extended Display Identification Data (EDID) for device identification.
That is, the HDMI® uses a DDC/EDID method of the Video Electronics Standard Association (VESA) for device identification.
The Display Data Channel (DDC) is used by the HDMI® source to read the EDID (or Enhanced Extended Display Identification Data (E-EDID)) from the HDMI® sink and the HDMI® repeater.
That is, the HDMI® sink and the HDMI® repeater include an EDID read only memory (EDID ROM) storing the EDID which is information regarding one's configuration or capability. The HDMI® source reads the EDID stored in each EDID ROM of the HDMI® sink and the HDMI® repeater via the DDC to recognize the configuration or the capability of the HDMI® sink and the HDMI® repeater based on the EDID. The EDID includes, for example, brand (manufacturer) of the HDMI® sink, model number, and format (e.g., image resolution) of signal supported by the HDMI® sink.
FIG. 1 shows an example of a connection of HDMI® devices via the HDMI® repeater including two output terminals.
An AV system in FIG. 1 includes a Blu-ray Disc® (BD) player 11, an AV amplifier 12, a TV (television receiver) 13, and a projector 14. Note that a system in this specification refers to a logical collection of multiple devices, regardless of whether devices of respective configurations are in a single case.
The BD player 11 is the HDMI® source, the AV amplifier 12 is the HDMI® repeater, and the BD player 11 and the AV amplifier 12 are connected by an HDMI® cable 15. The TV 13 and the projector 14 are both the HDMI® sink, the AV amplifier 12 and the TV 13 are connected by an HDMI® cable 16, and the AV amplifier 12 and the projector 14 are connected by an HDMI® cable 17.
The BD player 11 outputs an image and audio signal (also referred to below as AV signal) read from a BD as an HDMI® data stream. The AV amplifier 12 outputs the input HDMI® data stream to the TV 13 and the projector 14 simultaneously.
Two HDMI® outputs of the AV amplifier 12 are set as a primary output and a secondary output in advance. In the HDMI® specification, CEC control can be executed with only one HDMI® output. Thus, the CEC control is performed with the primary HDMI® output. In the AV system in FIG. 1, the TV 13 is connected to the primary HDMI® output of the AV amplifier 12, for example.
In this case, addressing for CEC in relation to the BD player 11 is performed only for the TV 13 connected to the primary HDMI® output to enable control with CEC. Meanwhile, addressing is performed for the projector 14 connected to the secondary HDMI® output only in relation to the AV amplifier 12 as the HDMI® repeater. In other words, the projector 14 does not exchange information with the BD player 11 connected to an HDMI® input of the AV amplifier 12.
By connecting the TV 13 and the projector 14 to the two HDMI® outputs of the AV amplifier 12, a user is expected to enjoy two display devices separately depending on contents or situation.
However, while a remote control of the TV 13 connected to the primary HDMI® output is capable of operations such as fast-forwarding of the BD player 11 and volume adjustment of the AV amplifier 12 with the CEC control of HDMI®, such operations are not performed with a remote control of the projector 14 connected to the secondary HDMI® output. Therefore, viewing with the projector 14 is extremely inconvenient.
One example solution to this problem is to enable CEC control of multiple HDMI® sinks by holding a physical address of an HDMI® source virtually (for example, see Japanese Unexamined Patent Application Publication No. 2008-153974).